Emissions carburetors and cold weather

[Craftsman GT]

Any suggestions for getting these to run better in cold weather? I've got a B&S 134202 5hp on my Simplicity Model D walk behind tractor that barely wants to run in this 30 degree weather right now. I got the plow on the tractor and fired it up to plow my driveway, and I have to run it at 3/4 choke just to get it to stay running smooth. If I fully open the choke it surges then dies. Even during the summer it has a lean surge til it's fully warmed up. It's pretty sad that we can't even get an engine that runs right anymore cause of these stupid emissions carbs...thanks epa.

[bgsengine]

Still using Summer blend fuel? or did you dump out your stored fuel and buy fresh winter blend? It makes a difference.

[Mek-a-nik]

Maybe the carb is needing a cleaning.

[Arkie]

Maybe the carb is needing a cleaning.

Right about maybe a cleaning. A low emission type carb also uses the low speed jet for enrichment at high speed operation for enrichment and if the low speed or idle port jet gets just little clogged it will lean out and all will suffer. (generally the old style adjustable jet carbs were not as critical of the low speed jet area and would not hunt and surge and lean out as much at high speed because of low speed jet restrictions even thou the carb would not idle well. (the old style were not low emission and a lean type Al Gore carb)
A hint that it's the low speed port is too hold the carb throttle or governor at low slow idle and if won't idle slow and smooth the carb is asking for attention. If it idles good but hunts and surges at high speed then it may be the high speed jet area or a partly clogged gas filter or filter screen.
On some of the small engine carbs you can search around online and find some hints about some carb mods to reduce hunting and surging, (and the enrichment mods are too the low speed jet)

Since your engine won't run at all at 30 degrees even after it's ran for awhile seems to indicate carb issues or intake manifold air leaks.
In summertime the engine should stabilize without choke after 30 sec and no longer than 1 minute.

[Craftsman GT]

Thanks everyone. The fuel was bought last week so I'm assuming it's winter blended. I changed the spark plug and all seems well so far (had a J8 in it). I'll update in a couple days and let you know how it is.

[Arkie]

Thanks everyone. The fuel was bought last week so I'm assuming it's winter blended. I changed the spark plug and all seems well so far (had a J8 in it). I'll update in a couple days and let you know how it is.

Yep, a bad spark plug really makes me feel weak after I've done all except overhaul the engine and finally found it was just a bad measely spark plug.

[KE4AVB]

Since your engine won't run at all at 30 degrees even after it's ran for awhile seems to indicate carb issues or intake manifold air leaks.
In summertime the engine should stabilize without choke after 30 sec and no longer than 1 minute.

Just had a similar problem which I haven't had since I flew N2326N and it was caused carburetor icing. Forgot all about this until reminded today by my own mower. It around freezing (32F), after it warmed up to around 45F things cleared up. This could have been the problem along with a borderline bad plug.

[Arkie]

Since your engine won't run at all at 30 degrees even after it's ran for awhile seems to indicate carb issues or intake manifold air leaks.
In summertime the engine should stabilize without choke after 30 sec and no longer than 1 minute.

Just had a similar problem which I haven't had since I flew N2326N and it was caused carburetor icing. Forgot all about this until reminded today by my own mower. It around freezing (32F), after it warmed up to around 45F things cleared up. This could have been the problem along with a borderline bad plug.

Some small engine eq have a heat shield around the carb so as it get warmed air from across the hot muffler.
I've tried using a hair dryer too warm the air on some of the low emission carbs intake air in cold weather just too see if the engine would stabilize faster during the first 2 minutes of warmup and really did not do any good until the engine itself got warm, although in severe cold weather (around 20 degrees and below) small emergency gen's with low emission carbs run and operate better if the engine is inside a enclosure where the carb can breathe the heated engines surrounding air. (exhaust properly vented outside)

Sure miss the old adjustable jet carbs. They have gone the way of dinosaurs! No one allowed to even clone one.

[Craftsman GT]

Hey everyone, sorry for the delay we haven't gotten any snow for awhile. Anyway, the engine completely died a few days ago and wouldn't even run. I started by replacing the diaphragm and still no start, so I popped the carb off and the screen over the main jet was clean but when I pulled it off I found a piece of brass from the jet blocking it. Looked like a manufacturing defect as it was left over flashing. I poked thru the the jet, put it back together and it's running the best it ever has. 20 degrees here right now.

[KE4AVB]

Very unusual...Most times I find rust particles blocking the jet from the lack of the tower screens being installed in the first place. As you said must have been since it was put into operation. This would explain the lean burn condition you had as it could have been partially blocking the all this time.

Glad you got it straighten now.

BTW I always install those screens when I rework these carburetors as the tanks tend to get rusty and the little fuel well tends have flakes in them for the carburetor to suck up. I even had drill out those factory sealing balls to clean out idle passages. Takes something between 7/64 and 1/8 chrome steel ball to replace it, most likely a 3mm one.